Magnetic window cleaning device

ABSTRACT

A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is manually moved along the windowpane. Each of the units comprises a rigid frame which holds an annular multipole permanent magnet and which has a flat surface facing the windowpane and a raised edge and a glide pin for spacing the flat surface from the windowpane. A cleaning pad such as a paper towel is held by a hinged pad holder over the flat surface and over the raised edge. The portion of the pad over the raised edge constitutes a primary cleaning surface and the portion of the pad which is over the flat frame surface constitutes a secondary cleaning surface, with the primary cleaning surface exerting greater pressure on the windowpane than the secondary cleaning surface. The annular magnets are magnetized in a plurality of circumferentially alternating poles and allow placing the master and slave units at different angles with respect to each other to facilitate cleaning of areas which may be difficult to reach otherwise.

ilnited States Patent [191 Doyel 1 May8,1973

[54] MAGNETIC WINDOW CLEANING DEVICE [76] Inventor: John S. Doyel, 404 W. 20th St., New

York, N.Y. 10011 [22] Filed: Dec. 3, 1971 [21] Appl. No.: 204,515

Primary Examinerl eon G. Machlin Att0rneyR0bert S. Dunham et a1.

[57] ABSTRACT A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is manually moved along the windowpane. Each of the units comprises a rigid frame which holds an annular multipole permanent magnet and which has a flat surface facing the windowpane and a raised edge and a glide pin for spacing the flat surface from the windowpane. A cleaning pad such as a paper towel is held by a hinged pad holder over the flat surface and over the raised edge. The portion of the pad over the raised edge constitutes a primary cleaning surface and the portion of the pad which is over the flat frame surface constitutes a secondary cleaning surface, with the primary cleaning surface exerting greater pressure on the windowpane than the secondary cleaning surface. The annular magnets are magnetized in a plurality of circumferentially alternating poles and allow placing the master and slave units at different angles with respect to each other to facilitate cleaning of areas which may be difficult to reach otherwise.

13 Claims, 10 Drawing Figures PATENTEU MY 8 75 SHEET 1 0F 3 M mmww f w y W PATENTEU HAY 8 I973 SHEET 3 (IF 3 MAGNETIC WINDOW CLEG DEVICE BACKGROUND OF THE INVENTION The invention is in the field of magnetic window cleaning devices and particularly in the field of magnetic window cleaning devices comprising a master unit and a slave unit which are held opposite each other across a windowpane by mutual magnetic attraction.

Magnetic window cleaning devices of various forms are disclosed in the prior art. Such devices comprise pairs of master and slave units, each unit provided with a permanent magnet or with an electromagnet, with the master unit moved by an operator along one side of a windowpane in a cleaning motion, and with the slave unit magnetically coupled with and following the master unit on the other side of the windowpane. Examples of such devices are DAndrea U.S. Pat. No. 2,507,559, Coleman U.S. Pat. No. 2,634,444, Narhaowski U.S. Pat. No. 2,668,975, Wiest, Jr. U.S. Pat. No. 2,707,298, Roesel, Jr. U.S. Pat. No. 3,208,090, I-Iogensen U.S. Pat. No. 2,805,438 and U.S. Pat. Nos. 3,296,645 and 3,600,737. The fundamental design goals of these devices are to provide adequate pressure upon the windowpane in order to ensure cleaning action, but to reduce the friction between the units of the device and the window so as to allow the slave unit to follow the master unit as the master unit is moved along the windowpane. Too little pressure upon the windowpane does not give adequate cleaning action and may result in magnetic decoupling between the master and slave units, with the slave unit falling away from the windowpane; and too much magnetic attraction between the master and slave units, and hence too much pressure upon the windowpane results in chatter", i.e., so such friction between the slave unit and the windowpane that the slave unit does not follow smoothly the motion of the master unit along the windowpane, but moves in a jerking motion. Excessive chatter may decouple the units.

There is a need to optimize the relationships between the degree of magnetic attraction of the master and slave units, the friction between the units and the windowpane, and cleaning action. There is also a need to provide a magnetic window cleaning device which is convenient to operate, gives adequate cleaning action and facilitates cleaning by providing a variety of relative positions between the master and slave units.

SUMMARY OF THE INVENTION A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which operative position the slave unit follows the master unit as the master unit is moved along the windowpane. Each unit comprises a rigid frame holding an annular magnet and having, on the side facing the windowpane, a substantially flat surface, a raised edge extending from that flat surface toward the window and a glide pin extending from the surface toward the windowpane. A cleaning pad is held by a hinged pad holder over at least a portion of the flat surface and over the raised edge.

When the unit is placed against a windowpane, the portion of the pad which is over the raised edge constitutes a primary cleaning surface and the portion of the pad which is over the flat surface constitutes a secondary cleaning surface. The unit rides over the windowpane mainly on the primary cleaning surface and on the glide pin, while the secondary cleaning contacts the windowpane but exerts lesser pressure thereon, and thus causes less friction. The flat surface below the cleaning pad may be irregular, for example it may have a plurality of indentations or a plurality of perforations, for the purpose of increasing the sliding friction between the cleaning pad and the flat surface, particularly when the cleaning pad is wet and expands into such indentations or perforations. The magnets used in the master and slave units are annular permanent magnets magnetized transversely to the windowpane in a circumferentially alternating pattern of poles. The magnets allow placing the master and slave units at different angles with respect to each other to facilitate cleaning of windowpane areas which may be difficult to reach otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a window-pane and a magnetic window cleaning device comprising a master unit and a slave unit magnetically coupled with each other in an operative position.

FIG. 2 is an elevational view of the master unit.

FIG. 3 is an elevational view of the slave unit.

FIG. 4 is a sectional view of the master unit taken along line 4-4 of FIG. 2 and a symmetrical sectional view of a slave unit in an operative position with respect to the master unit.

FIGS. 5, 6, 7 and 8 are respectively a plan view of a six-pole annular magnet used in the master and slave units, a plan view of a four-pole annular magnet, a perspective view of an annular magnet and a perspective view of backing plates for the annular magnet.

FIG. 9 is a perspective view of the windowpane facing portion of a frame used in the master and slave units of the window cleaning device.

FIG. 10 is an elevational view similar to FIG. 3 but showing a different embodiment of the slave unit.

DETAILED DESCRIPTION Referring to FIGS. 1, 2, 3 and 4, the invented magnetic window cleaning device comprises a master unit 10 and a slave unit 12 adapted to maintain with respect to each other an operative position shown, for example, in FIGS. 1 and 4 in which the units 10 and 12 are held by mutual magnetic attraction opposite each other across a windowpane M. The units 10 and 12 are connected by means of a safety string 16 which serves to lower the slave unit 12 to a suitable position at the inaccessible side of the windowpane M if need be, and to retrieve the slave unit 12 in case it disengages from the master unit 10 and falls away. Once the master unit 10 and the slave unit 12 are positioned as shown in FIGS. l

and 4, the master unit .10 is held by a handle 18 and moved along the windowpane 14 in cleaning motion. The slave unit 12 follows the master unit 10 because of magnetic coupling therewith. As described in detail later, the master and slave units 10 and 12 may be at different angles with respect to each other while in said operative position.

Each of the master and slave units 10 and 12 includes a substantially rigid frame made of material such as molded thermoplastic. A perspective view of the window facing side of the frame is shown in FIG. 9. The window facing sides of the frames in the master and slave units and 12 in identical, while the opposite sides differ slightly.

Referring to FIGS. 2, 4 and 9, the frame used in the master unit 10 comprises a substantially flat surface facing the windowpane l4 and disposed substantially parallel therewith, and a raised edge 22 extending from the flat surface 20 toward the windowpane 14. The flat surface 20 includes an aperture 20a for receiving the stem 24a of a glide pin having a glide head 24b facing the windowpane 14. The glide pin head 24b is made of material such as hard acetal resin characterized by good wearing quality and low friction. The frame is provided with a hinged cleaning pad holder 26 for holding a cleaning pad 28 over the flat surface 20 and over the raised edge 22 as shown in FIG. 4.

Referring to FIG. 4 which shows the master unit 10 in an operative position against the windowpane 14, it is seen that the flat surface 20 does not contact the windowpane 14. The windowpane 14 is contacted by the cleaning pad 28 and by the glide pin head 24b. The portion of the cleaning pad 28 which is over the raised edge 22 forms a primary cleaning surface, and the remaining window facing portion of the cleaning pad 28 forms a secondary cleaning surface, with the primary cleaning surface pressed against the windowpane 14 harder than the secondary cleaning surface, because of the raised edge. The master unit 10 thus rides on the windowpane 14 primarily on the portion of the cleaning pad 28 which is over the raised edge 22 and on the glide pin head 24b. The glide pin head 24b is made of low friction material, and thus helps reduce friction between the windowpane l4 and the master unit 10, while the portion of the cleaning pad 28 which is over the raised edge 22 acts as a scraper-like primary cleaning surface. The secondary cleaning surface, i.e., the remaining windowpane facing portion of the cleaning pad 28 presses against the windowpane 14 with less force per unit area and slides over the windowpane 14 more freely than .the primary cleaning surface.

In operation, the hinged cleaning pad holder 26 is opened as shown in FIG. 9 and a cleaning pad 28 which may be, for example, an absorbent paper towel is placed over thefla t frame area 20 and over the raised edge 22 and is then clamped in place by the hinged cleaning pad holder 26 as shown in FIG. 4. The cleaning pad 28 may then be wet with a cleaning solution or with water.

For the purpose of avoiding sliding between the secondary cleaning area portion of the cleaning pad 28 and the flat frame surface 20 while the master unit is moved along the windowpane 14, the flat surface 20 may be irregular so as to engage the secondary cleaning area portion of the pad 28. To this end, the flat surface 20 may be provided with a plurality of windowpane facing indentations 2012 or with a plurality of perforations 200. When the cleaning pad 28 is wet, it expands into the indentations 20b or the perforations 20c and is engaged by the edges thereof to prevent sliding of the pad 28 with respect to the flat surface 20 as the master unit 10 is moved along the windowpane 14. The flat surface 20 may be provided with alternate types of surface irregularities such as ridges, cerrations or surface grating for the purpose of increasing the friction between the surface 20 and the cleaning pad 28. The purpose of such surface irregularities is to make sure that the sliding friction between the flat surface 20 and the cleaning pad 28 is substantially greater than the friction between the windowpane 14 and the cleaning pad 28 such that the secondary cleaning surface of the pad 28 slides over the windowpane 14 while the cleaning pad 28 remains fixed with respect to the flat surface 20.

Referring to FIG. 2 which shows in plan view the side of the master unit 10 facing away from the windowpane l4, and to FIG. 4 which is a sectional view taken along line 4-4 of FIG. 2, the flat surface 20 is formed integrally with a side wall 30 which partially surrounds the flat surface 20 and extends rearwardly thereof, in a direction away from the windowpane 14, and with a plurality of ribs 32. The side wall 30 and the ribs 32 are for the purpose of ensuring that the master unit frame is substantially rigid and maintains the flat surface 20 spaced from the windowpane 14 when the master unit 10 rides on its primary cleaning surface, i.e., the cleaning pad portion over the raised edge 22, and on the glide pin head 24b as shown in FIG. 4.

The master unit frame also includes an annular chamber formed by two concentric circular walls 34 and 36 which are integrally formed with the flat surface 20 and extend rearwardly thereof in a direction'away from the windowpane 14. The annular chamber houses an annular magnet 38 which may be provided with metal backing plates 40 and 42. The annular chamber for the magnet 38 and for the backing plates 40 and 42 is capped, over the opening facing away from the windowpane 14, by a lid 44 attached to a cap 46 integrally formed with the wall 36 of the annular chamber for the magnet 38. The lid 44 is affixed to the cap 46 by means of a bolt 48 whose stem 48a passes through suitable apertures in the cap 44, the backing plates 42 and 40 and the cap 46. A handle 18 is affixed to the lid 44 in a suitable manner such as by gluing thereto. The handle 18 is provided with an eyelet 18a for attaching thereto one end of the safety string 16 which holds the master unit 10 and the slave unit 12 together.

Referring to FIG. 3 which shows in plan view the side of the slave unit 12 which faces away from the windowpane 14, and to FIG. 4 which shows a section taken along line 4--4 of FIG. 3, it is seen that the slave unit 12 is a mirror image of the master unit 10 with respect to the plane of the windowpane 14, except for the fact that the slave unit 12 has only one rib 32 as opposed to the five ribs 32 of the master unit 10, and except for the fact that the slave unit 12 has no handle 18. In the slave unit 12, the safety string 16 is attached to an eyelet 34a integrally formed with the wall 34 of the annular chamber for the magnet 38, v on the side thereof opposite the raised edge 22. The single rib 32 of the slave unit 12 is suflicient because the only force which may cause buckling of the flat surface 20 of the slave unit frame toward the windowpane 14 is the magnetic attraction between the slave unit 12 and the master unit tape 10, and this magnetic attraction is steady for a given thickness windowpane 14, while the ribs 32 of the master unit 10 must take the additional load of an operator pressing on the handle 18.

The magnets 38 which are used in the master unit 10 and the slave unit 12 are identical. Referring to FIG. 7,

the magnet 38 is annular in shape, resembling the magnets used in some common sound-reproducing speakers. The magnet 38 may be of ceramic magietizable one-piece material or of other magnetizable material which allows magnetization in a plurality of adjacent alternating poles. The magnet 38 is polarized perpendicularly to its flat surfaces in a plurality of circumferentially alternating poles. FIG. 5 for example illustrates an annular magnet 38 magnetized to have six circumferentially alternating north and south poles, while FIG. 6 illustrates an annular magnet 38 magnetized to have four circumferentially alternating north and south poles. Magnets with only two poles and magnets with more than eight or more poles may also be suitable, but it has been found through extensive experimentation that magnets with six poles, as illustrated in FIG. 5, are best for cleaning the types of windowpanes which are most commonly encountered. It has been found that four-pole magnets work better with windowpanes 14 which are thicker than the most often encountered type, while six-pole magnets work better with the type of windowpane 14 which is most often encountered. A four-pole magnet provides greater magnetic force than a six-pole magnet, which is preferable for thicker windowpanes, but is not desirable for normal thickness windowpanes because it causes excessive chatter, namely, the slave unit 12 does not follow the master unit 10 smoothly, but follows it in jerking motion. Excessive chatter results in disengagement between the master unit 10 and the slave unit 12. On the other hand, a six-pole magnet 38 as shown in FIG. 5, provides magnetic attraction which is adequate for maintaining magnetizing coupling between the master unit 10 and the slave unit 12, but does not cause chatter.

The magnets 38 of the master unit 10 and the slave unit 12 are oriented such that when the units are in a position shown in FIG. 4, each north pole of each of the magnets is directly opposite a south pole of the other magnet, and each south pole of each magnet is directly opposite a north pole of the other magnet. It is noted that when a six-pole magnet is used, there are six different angles between the master unit 10 and the slave unit 12 in which the units are stable, in an aperture position with respect to each other, and that when a four pole magnet of the type shown in H6. 6 is used, there are four different angles between the master unit 10 and the slave unit 12 at which the units are stable and in an operative position with respect to each other. The fact that the invented cleaning device allows for different angles between the master unit 10 and the slave unit 12 facilitates cleaning because it allows the primary cleaning area of the slave unit 12 to reach areas on the inaccessible side of the windowpane 14 which may not be possible to reach at the operating position shown in FIG. 4 because of obstructions on the accessible side of the windowpane 14 to the primary cleaning area 22 of the master unit 10.

FIG. 8 shows in perspective view a pair of ferromagnetic backing plates 40 and 42 which may be placed, as shown in FIG. 4, over the back surface of the magnet 38, i.e., the surface which faces away from the windowpane 14. The purpose of the backing plates 40 and 42 is to concentrate the magnetic flux for better magnetic attraction of the magnet 38. A single backing plate may be used instead of the plates 40 and 42, or the use of a backing plate may be altogether omitted if the magnets 38 provide adequate attraction without a backing plate.

FIG. 10 shows an alternate particular embodiment of a frame surface 20 with a particular type of surface irregularities serving the purpose of reducing the likelihood of sliding between the secondary cleaning area portion of the cleaning pad 28 and the flat frame surface 20 while the master unit is moved along the windowpane 14. The embodiment shown in FIG. 10 is the preferred embodiment of a frame surface 20. The flat frame surface 20 shown in FIG. 10 is provided with a plurality of slits 20d which are arranged in a concentric circle pattern. Each of the concentric circles comprises a plurality of adjacent slits 20d extending into the flat surface 20 and separated by solid portions of the flat surface 20. The slits 20d may extend completely through the flat surface 20, or may extend only partially into the flat surface. 20. What is important is that the slits 20d have relatively sharp edges where they join with the solid portion of the surface 20 facing the windowpane 14 such that the slits 20d can engage the secondary cleaning area portion of the cleaning pad 28 when the cleaning pad 28 is pressed against the flat surface 20.

I claim:

1. A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the windowpane, each of saidmaster and slave units comprising:

a substantially rigid frame having a substantially flat surface having sides and facing the windowpane when the unit is in said operative position and having along a single side thereof a raised hard and nan-ow edge extending from the plane of said'flat surface toward the windowpane when the unit is in said operative position;

a glide pin afiixed to said frameand having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, said glide pin being spaced from said raised edge and extending from the flat surface substantially as much as the raised edge;

a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position; and

a magnet and means for affixing the magnet to the frame, said magnet'being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween.

2. A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the windowpane, each of said master and slave units comprising:

a substantially rigid frame having a substantially flat surface facing the windowpane when the unit is in said operative position and having a raised edge extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, the windowpane facing surface of the raised edge being substantially smaller in area than said flat surface, wherein said substantially flat frame surface has an irregular window facing surface for increasing the sliding friction between said windowpane facing surface and said cleaning pad as the master and slave units are moved with respect to the windowpane in said operative position;

a glide pin affixed to said frame and having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said I operative position, said glide pin spaced from said raised edge;

a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position; and magnet'and means for affixing the magnet to the frame, said magnet being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween.

3. A magnetic window cleaning device as in claim 2 wherein said irregular surface comprises a surface provided with a plurality of perforations normal to the windowpane when the master and slave units are in their operative position with respect to each other, said perforations increasing the sliding friction between the windowpane facing flat surface of the frame and the cleaning pad.

5. A magnetic window cleaning device as in claim 1 wherein said magnet is a disk shaped permanent magnet with its axis perpendicular to the windowpane when the master and slave units are in their operative position with respect to each other, said magnet having a plurality of poles magnetized in a direction nonnal to the windowpane.

6. A magnetic window cleaning device as in claim 5 wherein said magnet is magnetized in six circumferentially alternating poles.

7. A magnetic window cleaning device as in claim 1 wherein said magnet is an annular permanent magnet magnetized in a plurality of circumferentially alternating poles.

8. A magnetic window cleaning device as in claim 7 wherein said annular magnet is a six-pole magnet.

9. A magnetic window cleaning device as in claim 1 wherein the windowpane facing surface of the cleaning pad portion which is over said raised edge of the frame and the window facing surface of the glide pin head define a plane which is spaced from and substantially parallel to the plane of said substantially flat surface of the frame when the master and slave units are in their operative position with respect to each other.

10. A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the window-pane, each of said master and slave units comprising:

a substantially rigid frame having a substantially fiat surface facing the windowpane when the unitis in said operative position and having a raised edge extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, the windowpane facing surface of the raised edge being substantially smaller in area than said flat surface;

a glide pin affixed to said frame and having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, said glide pin spaced from said raised edge;

a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position;-

a magnet and means for affixing the magnet to the frame, said magnet being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween; and

wherein said substantially flat frame surface facing the windowpane is provided with a plurality of surface irregularities, and wherein said cleaning pad is a water absorbent paper towel whose volume increases with the absorption of water, said surface irregularities engaging with a water soaked cleaning pad to resist sliding between the surface and the pad as the master and slave units are moved with respect to the windowpane while in their operative position with respect to each other.

lil

lar pattern.

13. A magnetic window cleaning device as in claim 10 wherein said surface irregularities are a plurality of slit shaped perforations arranged in a concentric circular pattern. 

1. A magnEtic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the windowpane, each of said master and slave units comprising: a substantially rigid frame having a substantially flat surface having sides and facing the windowpane when the unit is in said operative position and having along a single side thereof a raised hard and narrow edge extending from the plane of said flat surface toward the windowpane when the unit is in said operative position; a glide pin affixed to said frame and having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, said glide pin being spaced from said raised edge and extending from the flat surface substantially as much as the raised edge; a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position; and a magnet and means for affixing the magnet to the frame, said magnet being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween.
 2. A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the windowpane, each of said master and slave units comprising: a substantially rigid frame having a substantially flat surface facing the windowpane when the unit is in said operative position and having a raised edge extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, the windowpane facing surface of the raised edge being substantially smaller in area than said flat surface, wherein said substantially flat frame surface has an irregular window facing surface for increasing the sliding friction between said windowpane facing surface and said cleaning pad as the master and slave units are moved with respect to the windowpane in said operative position; a glide pin affixed to said frame and having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, said glide pin spaced from said raised edge; a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position; and a magnet and means for affixing the magnet to the frame, said magnet being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween.
 3. A magnetic window cleaning device as in claim 2 wherein said Irregular surface comprises a plurality of indentations into said substantially flat frame surface, said indentation facing the cleaning pad.
 4. A magnetic window cleaning device as in claim 2 wherein said irregular surface comprises a surface provided with a plurality of perforations normal to the windowpane when the master and slave units are in their operative position with respect to each other, said perforations increasing the sliding friction between the windowpane facing flat surface of the frame and the cleaning pad.
 5. A magnetic window cleaning device as in claim 1 wherein said magnet is a disk shaped permanent magnet with its axis perpendicular to the windowpane when the master and slave units are in their operative position with respect to each other, said magnet having a plurality of poles magnetized in a direction normal to the windowpane.
 6. A magnetic window cleaning device as in claim 5 wherein said magnet is magnetized in six circumferentially alternating poles.
 7. A magnetic window cleaning device as in claim 1 wherein said magnet is an annular permanent magnet magnetized in a plurality of circumferentially alternating poles.
 8. A magnetic window cleaning device as in claim 7 wherein said annular magnet is a six-pole magnet.
 9. A magnetic window cleaning device as in claim 1 wherein the windowpane facing surface of the cleaning pad portion which is over said raised edge of the frame and the window facing surface of the glide pin head define a plane which is spaced from and substantially parallel to the plane of said substantially flat surface of the frame when the master and slave units are in their operative position with respect to each other.
 10. A magnetic window cleaning device comprising a master unit and a slave unit adapted to maintain with respect to each other an operative position in which the units are held by mutual magnetic attraction opposite each other across a windowpane and in which the slave unit follows the master unit as the master unit is moved along the window-pane, each of said master and slave units comprising: a substantially rigid frame having a substantially flat surface facing the windowpane when the unit is in said operative position and having a raised edge extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, the windowpane facing surface of the raised edge being substantially smaller in area than said flat surface; a glide pin affixed to said frame and having a glide head extending from the plane of said flat surface toward the windowpane when the unit is in said operative position, said glide pin spaced from said raised edge; a cleaning pad and means for holding the pad onto the frame over the flat surface and over the raised edge, with the cleaning pad separating the flat area and the raised edge from the windowpane when the unit is in said operative position, the portion of the pad which is over the raised edge forming a primary cleaning area and the portion of the pad which is over the flat area forming a secondary cleaning area, with the glide pin and the primary cleaning surface pressing against the window with greater pressure per unit area than said secondary cleaning surface when the unit is in said operative position; a magnet and means for affixing the magnet to the frame, said magnet being of sufficient strength to maintain the master and slave units in said operative position by means of mutual magnetic attraction therebetween; and wherein said substantially flat frame surface facing the windowpane is provided with a plurality of surface irregularities, and wherein said cleaning pad is a water absorbent paper towel whose volume increases with the absorption of water, said surface irregularities engaging with a water soaked cleaning pad to resist sliding between the surface and the pad as the master and slave units are moved with respect to the windowpane while in their operative position with rEspect to each other.
 11. A magnetic window cleaning device as in claim 10 wherein said surface irregularities are a plurality of perforations facing the cleaning pad.
 12. A magnetic window cleaning device as in claim 10 wherein said surface irregularities are a plurality of slit shaped indentations arranged in a concentric circular pattern.
 13. A magnetic window cleaning device as in claim 10 wherein said surface irregularities are a plurality of slit shaped perforations arranged in a concentric circular pattern. 